SEMICONDUCTOR STRUCTURES COMPRISING CRYSTALLINE PrCaMnO (PCMO) FORMED BY ATOMIC LAYER DEPOSITION

ABSTRACT

Semiconductor structures include PrCaMnO (PCMO) material formed by atomic layer deposition. The PCMO material is formed by exposing a surface of a substrate to a manganese-containing precursor, an oxygen-containing precursor, a praseodymium-containing precursor and a calcium-containing precursor. The resulting PCMO material is crystalline.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/902,590, filed Oct. 12, 2010, pending, the disclosure of which ishereby incorporated herein in its entirety by this reference.

TECHNICAL FIELD

Embodiments of the present disclosure relate to semiconductor memoryfabrication and, more specifically, to methods for forming a crystallinePrCaMnO (PCMO) material by atomic layer deposition (ALD), and to relatedstructures and methods.

BACKGROUND

As conventional semiconductor memory, such as Flash memory and dynamicrandom access memory (DRAM), reach their scaling limits, research hasfocused on commercially viable low power, low operation voltage, highspeed and high-density non-volatile memory devices. One example of sucha non-volatile memory device is a variable resistance memory deviceincluding a programmable resistive memory material formed from amaterial exhibiting a very large negative magnetoresistance, oftenreferred to as a so-called “colossal magnetoresistance” (CMR) material.The CMR material may be connected to a current controlling device, suchas a diode, a field effect transistor (FET), or a bipolar junctiontransistor (BJT).

The resistance of the CMR material remains constant until a highelectric field induces current flow through the CMR material, resultingin a change in the CMR resistance. During a programming process, theresistivity of the memory resistor at the high field region near theelectrode changes first. Experimental data shows that the resistivity ofthe material at the cathode is increased while that at the anode isdecreased. During an erase process, the pulse polarity is reversed. Thatis, the designation of cathode and anode are reversed. Then, theresistivity of the material near the cathode is decreased, and theresistivity near the anode is increased.

One example of a CMR material is a manganese oxide of the generalformula R_(1-x)M_(x)MnO₃, wherein R is a rare earth element, M is ametal (e.g., calcium, strontium or barium), and x is a number from about0.1 to about 0.9. The CMR material is often referred to as “CMRmanganites.” CMR manganites exhibit reversible resistive switchingproperties, which may be used for low power, low operation voltage, highspeed and high-density memory applications.

PrCaMnO (PCMO) is a CMR manganite that is currently being explored dueto its potential for use in variable resistance memory devices.Amorphous PCMO may be deposited using a variety of methods, such asphysical vapor deposition (PVD), metal-organic chemical vapor deposition(MOCVD), and spin-coating. However, the resistive switchingcharacteristics of PCMO have been shown to improve as the PCMO reaches acrystalline phase. To convert amorphous PCMO to the crystalline phasesuch that the PCMO exhibits properties useful in variable resistancememory devices, the amorphous PCMO may be exposed to temperatures ofgreater than about 400° C. For example, after depositing the amorphousPCMO using a conventional CVD process, an annealing process is performedto convert the amorphous PCMO to crystalline PCMO by exposing theamorphous PCMO to a temperature of about 525° C.

Alternatively, an MOCVD process may be performed at increasedtemperatures (i.e., about 600° C.) to form crystalline PCMO. However,PCMO materials formed at temperatures greater than 550° C. may exhibitdecreased resistive switching characteristics. While not wishing to bebound by any particular theory, it is believed that decomposition of theMOCVD reactants may lead to uncontrolled growth of the PCMO. Precursorsfor depositing PCMO, such asbis(2,2,6,6-tetramethyl-3,5-heptanedionato)calcium (Ca(tmhd)₂),Pr(tmhd)₃, and Mn(tmhd)₂, have been explored for use in CVD processes.Due to their low reactivity, the precursors are deposited at increasedtemperatures and are codeposited with oxygen. Accordingly, depositingmaterials by ALD using such precursors may be difficult to control oraltogether unsuccessful.

Exposing semiconductor memory of memory device structures to increasedtemperatures during fabrication may cause degradation of heat-sensitivecomponents, such as metal wiring and interconnects. Thus, it is desiredto conduct semiconductor memory fabrication acts at relatively lowtemperatures (e.g., less than about 450° C.) to prevent suchdegradation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram illustrating a method of forming a crystallinePCMO material on a substrate by ALD in accordance with embodiments ofthe disclosure; and

FIGS. 2A and 2B are schematics illustrating a method of forming asemiconductor device in accordance with embodiments of the disclosure.

DETAILED DESCRIPTION

As used herein, the terms “atomic layer deposition” or “ALD” mean andinclude a vapor deposition process in which a plurality of separatedeposition cycles are conducted in a chamber. During each cycle, a metalprecursor is chemisorbed to a substrate surface, excess precursor ispurged out of the chamber, a subsequent precursor and/or reaction gas isintroduced to react with the chemisorbed species and excess reaction gasand byproducts are removed from the chamber. As compared to aconventional chemical vapor deposition (CVD) process where a desiredmaterial is deposited onto the substrate in a single cycle fromvaporized metal precursor compounds (and any reaction gases used) withina chamber, the multi-cycle ALD process enables improved control of layerthickness by self-limiting growth and minimizing detrimental gas phasereactions by separation of the reaction components. The term “atomiclayer deposition,” as used herein, includes “atomic layer epitaxy”(ALE), molecular beam epitaxy (MBE), gas source MBE, organometallic MBE,and chemical beam epitaxy when performed with alternating pulses ofprecursor compound(s), reaction gas(es), and purge (i.e., inert carrier)gas.

As used herein, the term “PCMO” means and includes a compound having thegeneral formula Pr_(1-x)Ca_(x)MnO₃, wherein x is a number of from about0.1 to about 0.9. Examples of stoichiometries for PCMO include, but arenot limited to, Pr_(0.7)Ca_(0.3)MnO₃, Pr_(0.5)Ca_(0.5)MnO₃ andPr_(0.67)Ca_(0.33)MnO₃.

As used herein, the term “CMR manganite” means and includes a compoundhaving the general formula R_(1-x)M_(x)MnO₃, wherein R is a rare earthelement, such as praseodymium (Pr), lanthanum (La) or neodymium (Nd), Mis a metal, such as calcium (Ca), strontium (Sr) or barium (Ba) and x isa number of from about 0.1 to about 0.9. Examples of CMR manganitesinclude, but are not limited to, PCMO, Pr_(1-x)Sr_(x)MnO₃ (PSMO),PrCaSrMnO₃ (PCSMO), La_(1-x)Sr_(x)MnO₃ (LSMO), La_(1-x)Ca_(x)MnO₃(LCMO), Nd_(1-x)Sr_(x)MnO₃ (NSMO) and Nd_(1-x)Sr_(x)MnO₃ (NSMO).

As used herein, the term “Cp” means and includes a cyclopentadienyl(C₅H₅) ligand having all five carbon atoms bound to a metal inη⁵-coordination by π bonding. The Cp ligand may be substituted orunsubstituted, such as with an alkyl group.

As used herein, the term “alkyl” means and includes a saturatedhydrocarbon chain having from one carbon atom to six carbon atoms inlength including, but not limited to, methyl, ethyl, propyl and butyl.The alkyl group may be straight-chain or branched-chain. Further, asused herein, “Me” represents methyl, “Et” represents ethyl, “iPr”represents isopropyl and “tBu” represents tert-butyl.

As used herein, the term “chemisorb” means and includes forming achemical linkage or bond between a chemical species and a surface, suchas that of a substrate. The term “chemisorbed,” as used herein, meansand includes a chemical species chemically linked or bonded to thesurface.

The following description provides specific details, such as materialtypes and processing conditions in order to provide a thoroughdescription of embodiments of the present disclosure. However, a personof ordinary skill in the art would understand that the embodiments ofthe present disclosure may be practiced without employing these specificdetails. Indeed, the embodiments of the present disclosure may bepracticed in conjunction with conventional fabrication techniquesemployed in the industry. In addition, the description provided belowdoes not form a complete process flow for manufacturing a semiconductordevice. The semiconductor device structures described below do not forma complete semiconductor device. Only those process acts and structuresnecessary to understand the embodiments of the present disclosure aredescribed in detail below. Additional acts to form a completesemiconductor device from the semiconductor device structures may beperformed by conventional fabrication techniques.

Methods for forming a PCMO material on a substrate by atomic layerdeposition (ALD) are disclosed. In particular, the methods may be usedto form a PCMO material having a crystalline structure (“crystallinePCMO”). The methods may include separately introducing amanganese-containing precursor, an oxygen-containing precursor, apraseodymium-containing precursor and a calcium-containing precursor toan exposed surface of the substrate to form the crystalline PCMOmaterial. Each of these precursors may be introduced to the substrateunder conditions that enable metal (i.e., manganese, praseodymium orcalcium) and/or oxygen from the precursor to chemisorb to the substrateor to react with another metal previously chemisorbed on the substrate,forming the PCMO material. Each of the precursors may be contacted withthe surface of the substrate at a temperature of less than about 450° C.and, thus, the method may be used to foam the crystalline PCMO materialon semiconductor structures without damaging or degrading exposed metalcomponents, such as copper interconnects or wiring.

The precursors for forming the PCMO material by ALD may includeprecursor compounds including a complex of a metal and a ligand. As anon-limiting example, the metal may include at least one of manganese,praseodymium and calcium and the ligand may include a substituted orunsubstituted cyclopentadienyl ligand (“Cp”) or a ketoimine ligand, suchas di-t-butyl ketoimine. Examples of precursors that may be usedinclude, but are not limited to, compounds having the formula M(Cp)_(n),M(MeCp)_(n), M(EtCp)_(n), M(iPrCp)_(n), M(tBuCp)_(n), M(Me₄C_(P))_(n),M(Me₅Cp)_(n), MCp(CO)_(n), MMeCp(CO)_(n) and M(tmhd)_(y), wherein Mrepresents at least one of manganese, praseodymium and calcium, and n ory are a number of ligands used to balance the charge of the metal. Thenumber of ligands n or y may be selected based on the valence state ofthe metal used in the precursor. By way of example, n or y may be aninteger ranging from 1 to 3.

As a non-limiting example, a manganese-containing precursor may includea compound having the formula MnCp(CO)₃, or MnMeCpCO₃. As anothernon-limiting example, a praseodymium-containing precursor may include acompound having the formula Pr(RCp)₃, wherein R is an alkyl group. Asyet another non-limiting example, a calcium-containing precursor mayinclude a compound having the formula Ca(RCp)₂, wherein R is an alkylgroup. Suitable alkyl groups may be selected based upon the molecularweight, size, branching or steric hindrance to impart the precursor witha desired volatility for use in the ALD process.

Additional metal-containing ALD precursors may be used in combinationwith, or in addition to, the specific precursors described herein. Suchadditional precursors are known in the art of ALD. While methods ofdepositing a PCMO material by ALD are specifically described herein, themethods may be used to deposit any CMR manganite material. For example,at least one of a strontium-containing precursor (e.g., Sr(tBuCp)₂ orSr(tmhd)₂), a lanthanum-containing precursor (e.g., La(iPrCp)₃), and aneodymium-containing precursor (Nd(iPrCp)₃) may be exposed to thesurface of the substrate to form a desired CMR manganite material.

As will be described, the precursors (i.e., the manganese-containingprecursor, the praseodymium-containing precursor and thecalcium-containing precursor) may, optionally, be vaporized anddeposited/chemisorbed substantially simultaneously with, and in thepresence of, an oxygen-containing precursor. For example, themanganese-containing precursor, the praseodymium-containing precursor,the calcium-containing precursor and the oxygen-containing precursor maybe sequentially introduced to the surface of the substrate to form thecrystalline PCMO material over the surface of the substrate. As anon-limiting example, the oxygen-containing precursor may include anoxygen-containing gas, such as ozone (O₃), oxygen (O₂) or nitric oxide(NO).

FIG. 1 is a flow diagram illustrating an embodiment of a method offorming a CMR manganite material or PCMO material by an ALD process. Asshown in FIG. 1, pretreatment 102, as depicted by dashed lines, of asubstrate surface may, optionally, be performed to increase reactivityof the substrate surface toward ALD precursors. The pretreatment 102 maybe performed on the substrate surface using a conventional process, suchas a polishing process, an etching process, an oxidation process, ahydroxylation process, or an annealing process. For example, thesubstrate surface may be pretreated to be terminated with at least onefunctional group, such as a hydroxyl group, an alkoxy group or a halidegroup.

In a first reaction phase 104 of the ALD process, themanganese-containing precursor may be introduced to a chamber in agaseous state and may chemisorb to the substrate surface. Themanganese-containing precursor may include any manganese-containingcompound suitable for use as an ALD precursor. For example, themanganese-containing precursor may include at least one ofcyclopentadienylmanganese tricarbonyl (CpMn(CO)₃),bis(cyclopentadienyl)manganese (MnCp₂),bis(ethylcyclopentadienyl)manganese ((CpEt)₂Mn),methylcyclopentadienylmanganese tricarbonyl ((CH₃C₅H₄)Mn(CO)₃), each ofwhich may be obtained commercially from Strem Chemicals, Inc.(Newburyport, Mass.). As a non-limiting example, themanganese-containing precursor may be introduced into the chamber byflowing an inert gas (e.g., nitrogen (N₂), argon (Ar), helium (He), neon(Ne), krypton (Kr), or xenon (Xe)) into the manganese-containingprecursor to form a mixture of the manganese-containing precursor andthe inert gas. As another non-limiting example, the manganese-containingprecursor may be dissolved in a solvent, such as tetrahydrofuran (THF),to form a solution of the manganese-containing precursor, which solutionmay be vaporized and supplied into the chamber. The manganese-containingprecursor may be supplied to the chamber as the mixture or the solution.The manganese-containing precursor supplied in this phase may beselected such that the amount of manganese-containing precursoravailable to bind to the substrate surface is determined by the numberof available binding sites and by the physical size of the chemisorbedspecies (including ligands). The manganese chemisorbed on the substratesurface during exposure to the manganese-containing precursor isself-terminated with a surface that is non-reactive with the remainingmanganese-containing precursor.

A gas removal phase 106 a that includes a pump and purge sequence may beperformed to remove excess manganese-containing precursor and/orbyproducts from the substrate surface. Pulsing with an inert gas removesthe excess manganese-containing precursor from the chamber, specificallythe manganese-containing precursor that has not chemisorbed to thesubstrate surface. Purging the chamber also removes volatile byproductsthat may be produced during the ALD process. In one embodiment, theinert gas may be nitrogen (N₂). The inert gas may be introduced into thechamber, for example, for about 10 seconds. After purging, the chambermay be evacuated or “pumped” to remove gases, such as the excessmanganese-containing precursor and the volatile byproducts. For example,the precursor may be purged from the chamber by techniques including,but not limited to, contacting the substrate surface and/or themanganese chemisorbed thereto with the inert gas and/or lowering thepressure in the chamber to below the deposition pressure of themanganese-containing precursor to reduce the concentration of themanganese-containing precursor contacting the substrate surface and/orchemisorbed species. Additionally, purging may include contacting thechemisorbed manganese with any substance that enables chemisorbedbyproducts to desorb and reduces a concentration of themanganese-containing precursor and the byproducts before introducinganother precursor. A suitable amount of purging to remove themanganese-containing precursor and the byproducts may be determinedexperimentally, as known to those of ordinary skill in the art. The pumpand purge sequences may be repeated multiple times. The pump and purgesequences may start or end with either the pump act or purge act. Thetime and parameters, such as gas flow, pressure and temperature, duringthe pump and purge acts may be altered during the pump and purgesequence.

Optionally, the first reaction phase 104 and the gas removal phase 106 amay be repeated any number of times, as indicated by arrow 105, to forma monolayer of manganese over the substrate surface. For example, thefirst reaction phase 104 and the gas removal phase 106 a may be repeatedin sequence from about two times to about five times to form themonolayer of manganese.

After the gas removal phase 106 a, a second reaction phase 108 of theALD process may introduce an oxygen-containing precursor into thechamber to form oxygen over the chemisorbed manganese. For example, theoxygen-containing precursor may include at least one of ozone, oxygenand nitric oxide. The oxygen and the chemisorbed manganese may react toform an intermediate material containing manganese and oxygen. Theintermediate material containing the manganese and the oxygen mayinclude, for example, manganese oxide or an intermediate reactivespecies containing the manganese and the oxygen. After exposure to theoxygen-containing precursor, reaction byproducts and the excessoxygen-containing precursor may be removed from the chamber using a gasremoval phase 106 b, including the pump and purge cycle as describedabove with respect to the gas removal phase 106 a. Optionally, thesecond reaction phase 108 and the gas removal phase 106 b may berepeated a number of times, as indicated by arrow 107, to form amonolayer of oxygen over the chemisorbed manganese. For example, thesecond reaction phase 108 and the gas removal phase 106 b may berepeated in sequence from about two times to about five times to formthe monolayer of oxygen. The monolayer of oxygen may react with thechemisorbed manganese, which chemisorbed manganese may include at leastone monolayer of manganese.

A third reaction phase 110 of the ALD process introduces thepraseodymium-containing precursor into the chamber to form praseodymiumover the intermediate material containing the manganese and the oxygen.The praseodymium-containing precursor may include Pr(iPrCp)₃ and may beintroduced into the chamber in a gaseous form. The Pr(iPrCp)₃ may beobtained commercially, for example, from Strem Chemicals, Inc. or AdekaCorporation (Tokyo, Japan). As a non-limiting example, thepraseodymium-containing precursor may be introduced into the chamber asa mixture with the inert gas or in solution with THF, as previouslydescribed. The praseodymium-containing precursor supplied in this phasemay be selected such that the amount of praseodymium-containingprecursor that may be available to bind to the substrate surface isdetermined by the number of available binding sites and by the physicalsize of the chemisorbed species (including ligands). The praseodymiumchemisorbed on the substrate surface during exposure to thepraseodymium-containing precursor is self-terminated with a surface thatis non-reactive with the remaining praseodymium-containing precursor.

For example, Pr(iPrCp)₃ may be exposed to the intermediate materialcontaining manganese and oxygen to form PrMnO₃ or a reactiveintermediate species containing the manganese, the oxygen andpraseodymium. After exposure to the praseodymium-containing precursor,reaction byproducts and the excess praseodymium-containing precursor maybe removed from the chamber using a gas removal phase 106 c includingthe pump and purge cycle described with respect to the gas removal phase106 a. Optionally, the third reaction phase 110 and the gas removalphase 106 c may be repeated a number of times, as indicated by arrow109, to form a monolayer of praseodymium over the intermediate materialcontaining the manganese and the oxygen. For example, the third reactionphase 110 and the gas removal phase 106 c may be repeated in sequencefrom about two times to about five times to form the monolayer ofpraseodymium. The monolayer of praseodymium may react with theintermediate material including the manganese and the oxygen, whichintermediate material may include at least one monolayer of each of themanganese and the oxygen.

A fourth reaction phase 112 of the ALD process may introduce thecalcium-containing precursor into the chamber to form calcium over theintermediate material containing the manganese, the oxygen and thepraseodymium. The calcium-containing precursor may include Ca(iPr₃ Cp)₂and may be introduced into the chamber to form the calcium over theintermediate material containing the manganese, the oxygen and thepraseodymium. As a non-limiting example, the calcium-containingprecursor may be introduced into the chamber as a mixture with the inertgas or in solution with THF, as previously described. The calcium andthe intermediate material containing the manganese, the oxygen and thepraseodymium may react to form the crystalline PCMO material. In someembodiments, a mixture of Ca(tBuCp)₂ and Sr(iPrCp)₃ may be exposed tothe intermediate material containing the manganese, the oxygen and thepraseodymium to form a crystalline PCSMO material. After exposure to thecalcium-containing precursor, reaction byproducts and the excesscalcium-containing precursor may be removed from the chamber by usingthe gas removal phase 106 d including the pump and purge cycle describedabove with respect to the gas removal phase 106 a. Optionally, thefourth reaction phase 112 and the gas removal phase 106 d may berepeated a number of times, as indicated by arrow 111, to faun amonolayer of calcium over intermediate material containing themanganese, the oxygen and the praseodymium. For example, the fourthreaction phase 112 and the gas removal phase 106 d may be repeated insequence from about two times to about five times to form the monolayerof calcium. The monolayer of calcium may react with the intermediatematerial including the manganese, the oxygen and the praseodymium, whichintermediate material may include at least one monolayer of each of themanganese, the oxygen and the praseodymium.

Exposure of the substrate surface to the precursors during the ALDprocess may be controlled to optimize the composition of the PCMOmaterial. For example, the crystalline PCMO material formed using theALD process may have a stoichiometry of Pr_(0.7)Ca_(0.3)MnO₃. Thecrystalline PCMO material may be formed on the substrate throughsuccessive or repetitive ALD cycles, as indicated by arrow 113, whereeach cycle deposits a thickness of the crystalline PCMO material. Adesired thickness of the crystalline PCMO material is achieved byperforming multiple, repetitious ALD cycles.

For the sake of simplicity, the precursors (i.e., themanganese-containing precursor, the oxygen-containing precursor, thepraseodymium-containing precursor and the calcium-containing precursor)are described in FIG. 1 as being introduced to the substrate surface ina particular order. However, the precursors (i.e., themanganese-containing precursor, the oxygen-containing precursor, thepraseodymium-containing precursor and the calcium-containing precursor)may be introduced to the substrate surface in any order.

During the ALD process, the pulse times for each of the precursors maybe from about 0.5 second to about 30 seconds. Each of the precursors(i.e., the manganese-containing precursor, the oxygen-containingprecursor, the praseodymium-containing precursor and the calciumprecursor) may be introduced to the substrate surface at a temperatureof less than about 450° C. and, more particularly, less than about 400°C.

Forming the PCMO material by ALD provides numerous advantages over otherprocesses of forming the PCMO material, such as MOCVD processes.Specifically, using ALD enables the PCMO material to be deposited in acrystalline state, rather than in an amorphous state. The crystallinePCMO material may be formed with a high degree of uniformity andconformality. Additionally, because the ALD process may be performed ata temperature of less than or equal to about 400° C., the crystallinePCMO material may be formed on a semiconductor or memory devicestructure without damaging heat-sensitive components, such as metalwiring and interconnects, as will be described. By utilizing the ALDprocess, the crystalline PCMO material may also be formed in situ at alow temperature.

FIGS. 2A and 2B illustrate a method of forming a semiconductorstructure, such as a variable resistance memory cell, including acrystalline PCMO material that may be formed according to embodiments ofthe present disclosure. For example, a semiconductor structure 200 maybe formed that includes a first electrode 204 in a substrate 206 and,optionally, an oxide material 205 (shown in broken lines) overlying thesubstrate 206. As a non-limiting example, the substrate 206 may be adoped polysilicon material. The first electrode 204 may be formed from aconductive material, such as copper, tungsten, nickel, tantalum,titanium, titanium nitride, aluminum, platinum, alloys thereof, amongstothers. The first electrode 204 may be formed using conventionalsemiconductor fabrication processes known in the art, which are notdescribed in detail herein. The oxide material 205 may be formed from arare earth metal oxide, such as zirconia (ZrO_(x)), yttrium oxide(YO_(x)), erbium oxide (ErO_(x)), gadolinium oxide (GdO_(x)), lanthanumaluminum oxide (LaAlO_(x)), and hafnium oxide (HfO_(x)) using aconventional deposition process, such as, a CVD process or an ALDprocess.

The semiconductor structure 200 may be placed in a chamber 208 (or mayremain in the chamber 208 after deposition of the oxide material 205)and a crystalline PCMO material 210 may be formed on the surface of thesemiconductor structure 200 using an ALD process such as that describedwith respect to FIG. 1. For example, a manganese-containing precursor,an oxygen-containing precursor, a praseodymium-containing precursor anda calcium-containing precursor may be separately and repeatedly exposedto the surface of the semiconductor structure 200 in the chamber 208 toform the crystalline PCMO material 210. The manganese-containingprecursor, the oxygen-containing precursor, the praseodymium-containingprecursor and the calcium-containing precursor may be introduced intothe chamber 208 in any order and may be introduced any number of timesto form a desired thickness of the crystalline PCMO material 210overlying the substrate 206. The ALD process may be performed at atemperature of less than about 450° C. and, thus, may form thecrystalline PCMO material 210 without damaging the first electrode 204or other conductive lines or wiring (not shown).

As shown in FIG. 2B, a second electrode 214 and, optionally, anotheroxide material 213 (shown in broken lines), may be formed over thecrystalline PCMO material 210 to produce the variable resistance memorycell 212. A portion of the crystalline PCMO material 210 may be removedusing conventional semiconductor fabrication techniques, which are notdescribed in detail herein. If present, the oxide material 213 may beformed from a rare earth metal oxide, such as zirconia (ZrO_(x)),yttrium oxide (YO_(x)), erbium oxide (ErO_(x)), gadolinium oxide(GdO_(x)), lanthanum aluminum oxide (LaAlO_(x)), and hafnium oxide(HfO_(x)) using a conventional deposition process, such as, a CVDprocess or an ALD process. The second electrode 214 may include aconductive material and may be formed over remaining portions of thecrystalline PCMO material 210 using conventional semiconductorfabrication techniques, which are not described in detail herein.

CONCLUSION

In one embodiment, the present disclosure includes a method of forming aPCMO material that includes forming a PCMO material on a substrate by anatomic layer deposition process.

In a further embodiment, the method of forming the PCMO materialincludes introducing a plurality of gaseous precursors to a surface of asubstrate to form a plurality of manganese, oxygen, praseodymium, andcalcium monolayers thereon and reacting the manganese, oxygen,praseodymium, and calcium monolayers to form a crystalline PCMOmaterial.

In yet another embodiment, the present invention includes asemiconductor structure including a crystalline PCMO material overlyinga substrate. The crystalline PCMO material is formed by separately andrepeatedly introducing a manganese-containing precursor, anoxygen-containing gaseous precursor, a praseodymium-containing precursorand a calcium-containing precursor to a surface of the substrate.

In yet another embodiment, the present invention includes a method offorming a semiconductor structure including forming at least oneelectrode on a substrate and separately and repeatedly exposing amanganese-containing precursor, an oxygen-containing gaseous precursor,a praseodymium-containing precursor and a calcium-containing precursorto a surface of the substrate to form a crystalline PCMO materialthereon. At least another electrode may be formed over the crystallinePCMO material.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, the invention is not intended to be limited to the particularforms disclosed. Rather, the invention is to cover all modifications,equivalents, and alternatives falling within the scope of the inventionas defined by the following appended claims and their legal equivalents.

What is claimed is:
 1. A semiconductor structure comprising: acrystalline PCMO material overlying a substrate, the crystalline PCMOmaterial formed by a process comprising: exposing a surface of thesubstrate to each of a praseodymium-containing precursor comprising acyclopentadienyl ligand (Cp), a calcium-containing precursor comprisinga cyclopentadienyl ligand (Cp), a manganese-containing precursor, and anoxygen-containing precursor to deposit a PCMO material in a crystallinestate over the substrate by an atomic layer deposition process conductedat a temperature of less than about 450° C.
 2. The semiconductorstructure of claim 1, further comprising a plurality of metalcomponents.
 3. The semiconductor structure of claim 1, wherein thecrystalline PCMO material comprises Pr_(0.7)Ca_(0.3)MaO₃,Pr_(0.5)Ca_(0.5)MnO₃, or Pr_(0.67)Ca_(0.33)MnO₃.
 4. The semiconductorstructure of claim 1, further comprising an oxide material over at leastone surface of the crystalline PCMO material.
 5. The semiconductorstructure of claim 4, wherein the oxide material comprises a rare earthmetal oxide.
 6. The semiconductor structure of claim 5, wherein the rareearth metal oxide comprises a material selected from the groupconsisting of zirconia (ZrO_(x)), yttrium oxide (YO_(x)), erbium oxide(ErO_(x)), gadolinium oxide (GdO_(x)), lanthanum aluminum oxide(LaAlO_(x)), and hafnium oxide (HfO_(x)).
 7. The semiconductor structureof claim 1, further comprising at least one electrode over thesubstrate.
 8. The semiconductor structure of claim 7, further comprisingat least another electrode over the crystalline PCMO material.
 9. Thesemiconductor structure of claim 1, wherein the semiconductor structurecomprises a variable resistance memory cell.
 10. The semiconductorstructure of claim 1, wherein the crystalline PCMO material is formed bya process wherein exposing the surface of the substrate to amanganese-containing precursor comprises exposing the surface of thesubstrate to a manganese-containing precursor comprising acyclopentadienyl ligand (Cp).
 11. The semiconductor structure of claim10, wherein the crystalline PCMO material is formed by a process whereinexposing the surface of the substrate to a manganese-containingprecursor comprising a cyclopentadienyl ligand comprises exposing thesurface of the substrate to a material having the formula MnCp(CO)₃. 12.The semiconductor structure of claim 10, wherein the crystalline PCMOmaterial is formed by a process wherein each of the manganese-containingprecursor, the praseodymium-containing precursor, and thecalcium-containing precursor comprise at least one compound having theformula M(MeCp)_(n), M(EtCp)_(n), M(iPrCp)_(n), M(tBuCp)_(n),M(Me₄Cp)_(n), M(Me₅Cp)_(n), and MCp(CO)_(n), wherein M representsmanganese, praseodymium, or calcium and n represents a number of ligandsused to balance the charge of the manganese, praseodymium, or calcium.13. The semiconductor structure of claim 1, wherein the crystalline PCMOmaterial is formed by a process wherein exposing the surface of thesubstrate to the oxygen-containing precursor comprises exposing thesurface of the substrate to at least one material selected from thegroup consisting of ozone, oxygen, and nitric oxide.
 14. Thesemiconductor structure of claim 1, wherein the crystalline PCMOmaterial is formed by a process wherein exposing the surface of thesubstrate to the praseodymium-containing precursor comprises exposingthe surface of the substrate to a praseodymium-containing precursorhaving the formula Pr(RCp)₃, wherein R is an alkyl group.
 15. Thesemiconductor structure of claim 1, wherein the crystalline PCMOmaterial is formed by a process wherein exposing the surface of thesubstrate to the calcium-containing precursor comprises exposing thesurface of the substrate to a calcium-containing precursor having theformula Ca(RCp)₂, wherein R is an alkyl group.
 16. The semiconductorstructure of claim 1, wherein the crystalline PCMO material is formed bya process wherein exposing the surface of the substrate to each of thepraseodymium-containing precursor, the calcium-containing precursor, themanganese-containing precursor, and the oxygen-containing precursorcomprises separately exposing the surface of the substrate to each ofthe praseodymium-containing precursor, the calcium-containing precursor,the manganese-containing precursor, and the oxygen-containing precursor.17. A semiconductor structure comprising: at least one electrode on asubstrate; and a crystalline material overlying at least a portion ofthe substrate, the crystalline material comprising manganese, oxygen,praseodymium, and calcium, and formed by a process comprising:separately and repeatedly exposing the substrate at a temperature ofless than about 450° C. to a manganese-containing precursor, anoxygen-containing gaseous precursor, a praseodymium-containingprecursor, and a calcium-containing precursor, wherein thepraseodymium-containing precursor comprises the formula Pr(RCp)₃,wherein the calcium-containing precursor comprises the formula Ca(RCp)₂,wherein Cp comprises a cyclopentadienyl ligand, and wherein each Rindependently comprises an alkyl group.
 18. The semiconductor structureof claim 17, further comprising an oxide material disposed over at leastone surface of the crystalline material.
 19. The semiconductor structureof claim 17, further comprising at least another electrode disposed overthe crystalline PCMO material.
 20. The semiconductor structure of claim17, wherein the semiconductor structure comprises a variable resistancememory cell.
 21. A semiconductor structure comprising: a crystallinePCMO material overlying a substrate, the crystalline PCMO materialformed by a process comprising: introducing a plurality of gaseousprecursors to a surface of the substrate at a temperature of less thanabout 450° C. to form a plurality of manganese, oxygen, praseodymium,and calcium monolayers thereon, the plurality of gaseous precursorscomprising a praseodymium-containing precursor comprising acyclopentadienyl ligand (Cp) and a calcium-containing precursorcomprising a cyclopentadienyl ligand (Cp); and reacting the plurality ofmanganese, oxygen, praseodymium, and calcium monolayers to form acrystalline PCMO material without forming an amorphous PCMO material.